Measuring optical reflectivity of graphene films using compensated Fabry-Perot interferometry

Abstract

Graphene optical applications rely on its exceptional optical characteristics, for which accurate measurement of graphene reflectivity is critical. Fabry-Perot (F-P) interferometry is a standard reflectivity measurement method with a simple structure, fast measurement speed, and high system plasticity. However, a strong coupling relationship exists between the coupling coefficient and the reflectivity of graphene in the F-P interferometry measurements of graphene reflectivity. Therefore, a method for measuring the reflectivity of thin graphene films using F-P interferometry with a compensation factor is proposed and experimentally demonstrated. Four alternative graphene film reflectivity solution models are established within four different F-P cavity lengths. The experimental results of the solution model with cavity lengths of 50–100 μm show that the average reflectivity of single-layer, two-layer, five-layer, eight-layer, and ten-layer graphene films are 0.0131%, 0.101%, 0.793%, 1.335%, and 1.978% with the errors of 0.7%, 1.0%, 1.0%, 1.1%, and 1.1%, respectively. Meanwhile, the standard deviation of graphene reflectivity increases with the number of graphene layers. The highly consistent experimental data and comparative results confirmed the accuracy of our method. This method proposed in this paper could be further extended to measure the reflectivity of other 2-D materials.